The invention concerns flat flexible cable (FFC), both laminated and extruded, and especially with connectors or strip terminals or the like, for electrical contacting according to the introductory part of claim 1.
Laminated electrical flat conductors essentially consist of a flexible support sheet with a preformed conductor set applied on it. The conductor set consists of individual conductor tracks. The individual conductor tracks are individually insulated from each other, i.e., arranged at a spacing relative to each other and have a rectangular cross section with sometimes different dimensions and are therefore also called rectangular conductors. The tops of the conductor tracks are electrically insulated, sheets being used in particular, which are laminated onto the conductors by means of appropriate adhesives, and the bottoms onto the support sheet. Such flexible conductors, called FFC (flexible flat cable) in technical jargon, are used to an increasing degree in automobile manufacture as a replacement for ordinary cable harnesses consisting of round conductors.
Another method for producing extruded flat flexible cable consists of enclosing the conductor tracks by an extrusion process with an electrically insulating sheath, in which the shape and properties of the finished extruded flat flexible cable correspond at least essentially to the shape and properties of the finished laminated flat flexible cable.
Various advantages are gained during use of FFC in contrast to ordinary cable harnesses: by using rectangular conductors as conductor tracks greater amounts of current can be transferred at equal cross-sectional area in comparison with round conductors so that a weight reduction and a reduction in space requirements is obtained, especially in automobile manufacture. The accessibility and especially the flat configuration of such a cable harness are also advantageous, since this type of cable harness can also be mounted behind coverings with limited design depth.
A shortcoming in such flat flexible cables (and in both types) has thus far been the problem of mechanical stability during transport of such flat flexible cables in the state with the insulation removed, since the individual rectangular conductors do not exhibit significant mechanical stability and resist automated handling and electrical connection of such flat flexible cables with circuit boards in control equipment, with other flat conductors or in a transition to ordinary round conductors. The mechanical vulnerability of the stripped rectangular conductors no longer connected via the laminate has also turned out to be inconvenient.
The task of the present invention is to devise an appropriate preparation of flat flexible cables in the contacting area through which simple and reliable transport is also ensured before contacting and reliable and permanent contacting with simultaneous relief of tension and avoidance of damage to the flat cable during handling.
According to the invention, the task is solved by the expedients of the characterizing part of claim 1, namely by the fact that removal of the insulation of the flat flexible cable occurs in an area that lies at a spacing from the end of the flat flexible cable. By this expedient, the actual end of the flat flexible cable is retained as a unit and therefore has high mechanical stability and shape retention in comparison with the individual conductor tracks, which significantly facilitates handling during introduction of the conductor track into the connector and at the same time solves the problem of relieving tension on the conductor track.
The invention also concerns a connector for reliable contacting and fixation of such a flat flexible cable which also has tension relief.
This task is solved according to the invention in that the connector in the region of each rectangular conductor being contacted, in which it is not stripped in the end region, has at least one point and/or at least one edge running essentially across the rectangular conductor, which executes a movement toward the rectangular conductor during contacting of the flat flexible cable so that the point or edge contacts through the sheet covering the rectangular conductor on this side and deforms.
In this manner, the tensile forces occurring during operation are directly transferred to the conductor track and sufficient tension relief occurs. By using the connector according to the invention, which jointly contacts several rectangular conductors under practical conditions, even if they are electrically separated from each other, compensation for any tolerance-related, uniform holding forces occurs, since because of the piece of support sheet left on the end of the flat flexible cable and the cover sheet, a mechanical compensation can occur that would be impossible in the individual conductors.
In one embodiment of the invention, the contacts situated in the connector are guided via the points or edges and contact the rectangular conductors in the region in which the two sheets are removed, both from the top and from the bottom. By movement in the region of the point or edge an easy glancing movement occurs with a loop-like design of the contacts on the connector side during locking of the connector so that any contaminants situated on the surface of the rectangular conductor are removed and contacting is improved.
In another embodiment of the invention, it is proposed the components that carry the protrusion or edge and the conductor have on the end facing the flat flexible cable a corrugation running across the direction of the rectangular conductor which contacts the flat flexible cable in the region in which both the support sheet and the cover sheet (or the extruded insulation material) are left, i.e., on the other side of the contact window. Because of this, penetration of dirt and contaminants into the contact region can be reduced and additional fixation of the flat flexible cable occurs in the contact area so that the actual contact surface is shielded mechanically on both sides.
Movement of the component that carries the point or edge and preferably also the contacts and the corrugation can occur in known fashion by cams, wedges or snaps of the housings and is no problem for one skilled in the field of connector design.
In order to prevent a common error that invariably occurs during mounting of connectors on cable ends, especially under the hampered incorporation conditions in automobile manufacture, it is proposed in one embodiment of the invention to arrange the actual connector in a housing and apply hooks laterally to the housing that are pivoted during insertion of the end of the flat flexible cable from the insulation piece that was left right on the end of the cable in a region from 2 to 3 mm and, in so doing, engage behind the end of this insulation piece on the window side and fix its position. Because of the position of these hooks lying at least partially outside of the housing, correct assembly of the flat flexible cable in the connector can be concluded even before it is closed and fixed.
It is proposed in one embodiment of this variant that by pivoting of the two hooks in the assembly position an element that is required for performance in contacting, for example, a locking pin or the like, is released so that the connector can only be closed or the inserted flat flexible cable only fixed when it is correctly and fully inserted into the connector.
It is also possible by the expedient according to the invention to simultaneously contact all conductor tracks or at least a larger number of conductor tracks of a flat flexible cable so that the work time connected with this is shortened, on the one hand, and errors can be avoided, on the other, since correct introduction of the end of the flat flexible cable into the connector can be better controlled and checked, the more bulky and mechanically stable this end is.
The invention also permits simple transition to round cable, since only the individual contacts (pins) of the connector need be connected to corresponding strands of a round cable. The connector can also directly be a part of a circuit board or current consumer.